catena-Poly[[cobalt(II)-μ-aqua-di-μ-butanoato-κ2 O:O′;κ2 O:O] 0.7-hydrate]

In the title coordination polymer, {[Co(C3H7COO)2(H2O)]·0.7H2O}n, the Co2+ cation is coordinated by four bridging butanoate anions and two bridging water molecules in a severely distorted octahedral geometry. The Co2+ cations are linked by means of bridging ligands into polymeric chains along [010]. These chains are further connected to each other through hydrogen bonds involving partially occupied disordered water molecules; thus, sheets parallel to (001) are formed. One of the positions of disordered water O atom lies on a twofold axis. Two atoms of the aliphatic chain of one of the butanoate anions are disordered over two positions each.

In the title coordination polymer, {[Co(C 3 H 7 COO) 2 (H 2 O)]Á-0.7H 2 O} n , the Co 2+ cation is coordinated by four bridging butanoate anions and two bridging water molecules in a severely distorted octahedral geometry. The Co 2+ cations are linked by means of bridging ligands into polymeric chains along [010]. These chains are further connected to each other through hydrogen bonds involving partially occupied disordered water molecules; thus, sheets parallel to (001) are formed. One of the positions of disordered water O atom lies on a twofold axis. Two atoms of the aliphatic chain of one of the butanoate anions are disordered over two positions each.
The crystal structure of the title compound contains one independent Co 2+ cation coordinated by four O atoms of four bridging butyrates and two O atoms of bridging water molecules in a severely distorted octahedral coordination (Fig. 1).
The cis-angles about the Co atom range from 80.77 (9) to 106.47 (9)°, the Co-O bond lengths are in the range of 2.027 (2) -2.217 (2) Å; this data correlates with the angles and the distances in cobalt(II) acetate dihydrate with similar structure (Jiao et al., 2000) as well as isostructural cobalt(II) propionate dihydrate (Fischer et al., 2010). are produced (Fig. 2). The O61 atom of disordered solvate water molecule occupies a special position on the twofold axis.

Experimental
To a solution of butyric acid (8.8 g, 100 mmol) in water (50 ml), an excess of fresh cobalt(II) carbonate hydrate, CoCO 3 .xH 2 O (x=0.35-1.00), (8.0 g, approximately 60 mmol) was added. The reaction mixture was periodically stirred in ultrasonic bath at room temperature until the liberation of carbon dioxide ceased. The unreacted CoCO 3 .xH 2 O was removed by filtration, and the filtrate was allowed to stand at room temperature for slow evaporation. After a few days, red single crystals of the title compound suitable for X-ray diffraction study precipitated. Yield 82%.

Refinement
The sup-2 the riding model approximation, with U iso (H) set to 1.5U eq (C) and C-H 0.96Å for the methyl groups and 1.2U eq (C) and C-H 0.97 Å for the methylene groups.